Definition:
Niemann-Pick Type A, sometimes referred to as infantile Niemann-Pick disease, results from deficient activity of acid sphingomyelinase (ASM), which metabolizes sphingomyelin. In Niemann-Pick type A, sphingomyelin accumulates within cells, eventually leading to their death. Children with Niemann-Pick A have very little residual activity of ASM.

Niemann-Pick Disease Types A and B both result from deficient activity of ASM. The degree of deficiency is most marked in Niemann-Pick A and less severe in Niemann-Pick B. Niemann-Pick C does not result from an enzyme defect but is caused by mutations in two separate genes, both of which affect the trafficking of lipids within cells.

Niemann-Pick Disease Type A affects all races and ethnicities but is more common among the Ashkenazi Jewish population. The carrier frequency for either Niemann-Pick Disease Type A or B is estimated at one in one thousand Ashkenazi Jews. Niemann-Pick Type A is more frequent than Niemann-Pick Type B and accounts for 60% of the cases of ASM deficiency.

Symptoms:
The symptoms of Niemann-Pick Type A manifest in the first few months of life. At six months of age, feeding difficulties occur, along with progressive loss of early motor skills and enlargement of the abdominal organs.  The skin may also discolor, taking on a brownish to yellowish hue. Approximately half of affected children will develop a cherry-red spot in their eye.  As the disease progresses, motor and mental functions decline.

Inheritance Pattern:
Niemann-Pick Type A is an autosomal recessive disorder.

Life Expectancy:
Life expectancy for Niemann-Pick Type A is commonly between two and three years of age.

Diagnosis and Testing:
Niemann-Pick Disease Type A is diagnosed by measuring the activity of acid sphingomyelinase (ASM) in blood cells or tissue biopsies. Typically, patients with Niemann-Pick A have less than one percent of normal activity.  Prenatal screening can be performed using enzyme assay on fetal fluid or cells but is most accurate when molecular analysis for mutation in the ASM gene is performed.

Treatment:
There is no effective treatment for children affected by Niemann-Pick Type A. Symptom management includes controlling the associated respiratory, cardiovascular, and gastroenterology symptoms. Nutritional and physical therapy are additional supportive treatment options to assist with feeding difficulties and the decline of motor skills in children affected by Niemann-Pick disease Type A.

Patient Groups:
National Niemann-Pick Disease Foundation
P.O. Box 49
401 Madison Ave. Ste B
Fort Atkinson, WI 53538
www.nnpdf.org
tel: (920) 563-0930
fax: (920) 563-0931
Nadine Hill, Director of Family Services
nnpdf@nnpdf.org

National Tay-Sachs & Allied Diseases Association
2001 Beacon Street, Suite 204
Boston, MA 02135
www.ntsad.org
tel: (800) 906-8723
fax: (617) 277-0134
Sue R. Kahn, Executive Director
info@ntsad.org